* The physical mail is moving from where I am travelling to where the recipient is back home. It has to travel, just like I am.
* The best post cards are cramped with text.
* postmarks: (for me at least) you see where it was mailed from and when, additional ties to the time and place when it was written. A postmark from wherever the postagram warehouse is located isn't as interesting as the Paris mail exchange or the airmail stamp from Dehli.
seems to me like they've missed what gives value to postcards to me: their timeliness & physical history. No one really looks at the picture anyway, that's incidental, it's the message that's important.
I always put a _lot_ more than 140 characters on the back of a postcard. I put more than 140 charters just into the "DO NOT WRITE IN THIS SPACE" space on the postcard. Postcards aren't about the picture, they're about sending a message from a specific time and place, forward to a person in a different place.
So, this is a good idea, but won't replace actual postcards for me. I could see using it for a number of other things, but I don't think this is in any way "at least 1,000 times better" than a long, thoughtful note crammed onto the back of some cheap cardstock you bought for a quarter at the beach. EDIT: spelling.